Indexing apparatus for tool holders of machine tools

ABSTRACT

THE TURRET-SHAPED HOLDER FOR A SET OF TOOLS IN A MACHINE TOOL IS INDEXIBLE BY AN APPARATUS WHICH EMPLOYS A PAIR OF CLUTCH MEMBERS ONE OF WHICH IS ROTATABLE WITH REFERENCE TO THE OTHER CLUTCH MEMBER TO THEREBY DISENGAGE A FACE GEAR ON THE HOLDER FROM A STATIONARY FACE GEAR SO THAT THE HOLDER CAN BE ROTATED TO A SELECTED ANGULAR POSITION. THE ROTARY CLUTCH MEMBER MESHES WITH A SLEEVE WHICH ROTATABLE SURROUNDS THE SHAFT OF THE HOLDER AND MOVES THE HOLDER AXIALLY IN RESPONSE TO ROTATION AND/OR AXIAL MOVEMENT OF THE ROTARY CLUTCH MEMBER. A CLUTCH IN THE VARIABLE-SPEED DRIVE WHICH ROTATES THE HOLDER WHEN THE FACE GEARS ARE DISENGAGED FROM EACH OTHER ALLOWS FOR LIMITED ROTATION OF THE HOLDER WHEN THE TEETH OF THE FACE GEARS MESH WITH EACH OTHER. A PACKAGE OF DISHED SPRINGS URGES THE FACE GEARS APART AND MAINTAINS THE CLAWS OF THE CLUTCH MEMBERS IN ABUTEMENT WITH EACH OTHER. THE SYSTEM WHICH SELECTS THE ANGULAR POSITIONS OF THE HOLDER HAS A SET OF CAMS WHICH ARE ROTATABLE WITH THE SHAFT OF THE HOLDER. SUCH SYSTEM INSURES THAT A SELECTED TOOL ON THE HOLDER IS MOVED TO ITS OPERATIVE POSITION BY THE SHORTEST POSSIBLE ROUTE SO THAT THE SHAFT OF THE HOLDER NEED NOT ROTATE THROUGH MORE THAN 180 DEGREES.   D R A W I N G

Feb. 27, 1973 H. LAHM 3,717,912

INDEXING APPARATUS FOR TOOL HOLDERS OF MACHINE TOOLS Filed Sept. 16, 1971 5 Sheets-Sheet 1 Fig.1

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INDEXING APPARATUS FOR TOOL HOLDERS OF MACHINE TOOLS Filed Sept. 16, 1971 5 Sheets-Sheet 5 Fig.5 Fig.9

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Heinrich Lahm his Attorney United States Patent O 3,717,912 INDEXING APPARATUS FOR TQOL HOLDERS OF MACHINE TOOLS Heinrich Lahm, Essliugcn-Sirnau, Germany, assignor to Index-Werke KG Hahn & Tessky, Esslingen, Germany Filed Sept. 16, 1971, Ser. No. 181,119 Claims priority, application Germany, Mar. 3, 1971,

P 21 16 147.3 Int. Cl. B231) 7/04 US. Cl. 29-69 26 Claims ABSTRACT OF THE DISCLOSURE The turret-shaped holder for a set of tools in a machine tool is indexible by an apparatus which employs a pair of clutch members one of which is rotatable with reference to the other clutch member to thereby disengage a face gear on the holder from a stationary face gear so that the holder can be rotated to a selected angular position. The rotary clutch member meshes with a sleeve which rotatably surrounds the shaft of the holder and moves the holder axially in response to rotation and/ or axial movement of the rotary clutch member. A clutch in the variable-speed drive which rotates the holder when the face gears are disengaged from each other allows for limited rotation of the holder when the teeth of the face gears mesh with each other. A package of dished springs urges the face gears apart and maintains the claws of the clutch members in abutment with each other. The system which selects the angular positions of the holder has a set of cams which are rotatable with the shaft of the holder. Such system insures that a selected tool on the holder is moved to its operative positioin by the shortest possible route so that the shaft of the holder need not rotate through more than 180 degrees.

BACKGROUND OF THE INVENTION The present invention relates to indexing apparatus for use in machine tools or the like, and more particularly to improvements in indexing apparatus for tool holders of turning machines or the like. Still more particularly, the invention relates to improvements in automatic indexing apparatus which are designed to move a selected grinding, milling, boring or other tool to its operative position in response to a signal to the control system of such apparatus.

An important requirement for the satisfactory operation of indexing apparatus for rotatory tool holders is that a selected tool should be rapidly moved to its operative position and that it should be safely and reliably held in such position during engagement with and during removal of material from a workpiece even if the tool is subjected to considerable stresses during such engagement with the workpiece. Another important requirement for satisfactory operation of such apparatus is that the selected tool should be fixed and held in an accurately determined operative position in order to insure controlled removal of material from a workpiece, for example, from a workpiece which is held in the chuck of and is rotated by a work spindle. As a rule, the presently known indexing apparatus are equipped with means for rapidly rotating the tool holder to a position in which the selected tool is located close to its operative position and for thereupon completing the angular displacement of the tool holder at a greatly reduced speed in order to move the selected tool all the way to the respective operative position. It is further customary to provide such conventional indexing apparatus with mechanical detent means or locking means in order to safely hold the selected tool in its operative position during engagement with the workpiece.

ICC

A presently known indexing apparatus for rotary tool holders of machine tools operates in the following way: When a fresh tool has been selected for movement to its operative position, the motor of the indexing apparatus is started and accelerated to a high operating speed immediately after the locking action upon the tool holder is terminated. The operating speed of the motor is reduced shortly before the selected tool reaches its operative position. During such operation at the reduced speed, the tool holder passes beyond a locating and arresting bolt. The direction of rotation of the motor is thereupon changed so that the tool holder rotates in the opposite direction until a surface thereon comes into abutment with the arresting bolt. The motor is then prevented from rotating the tool holder beyond the thus determined selected position and is arrested by a limit switch which is actuated by an axially biased drive shaft. The tool holder is locked in the freshly selected angular position by a claw clutch having two clutch elements provided with claws having inclined front surfaces.

Another known indexing apparatus employs a Geneva movement which exhibits the advantage that the tool holder need not be rotated by a complicated variablespeed drive. However, the Geneva movement decelerates the tool holder to zero speed whenever a tool reaches its operative position so that, when the tool holder must be rotated through an anglewhich necessitates the movement of se eral successive tools to and from their operative positions, the interval which elapses during such rotation of the tool holder is very long. Also, the tool holder is moved in jerky fashion because it is repeatedly decelerated to zero speed and accelerated to maximum speed.

Another serious drawback of the above described conventional indexing apparatus is that they must be provided with rather complicated position selecting and control systems and also that their parts are subjected to considerable wear.

It is further known to provide an indexing apparatus with a hydraulic tandem cylinder which serves to unlock the tool holder prior to rotation and to lock it when a selected tool dwells in its operative position. Such apparatus are rather sensitive to stresses which are transmitted to the selected tool by a workpiece during removal of material. Also, the indexing apparatus must be provided with costly and complicated safety devices to prevent unlocking of the tool holder when the machine tool is idle. Furthermore, special devices must be provided to insure proper intermeshing of the gears which locate the tool holder in selected angular position and while the selected tool engages a workpiece.

SUMMARY OF THE INVENTION An object of the invention is to provide a relatively simple, compact and reliable indexing apparatus which can be used to move any one of several tools on a rotary tool holder to the operative position with minimal delay even if the selected tool happens to dwell at a considerable distance from the operative position.

Another object of the invention is to provide an indexing apparatus wherein at least some of the parts need not be machined with a very high degree of precision without affecting the accuracy of positioning of selected tools in their operative positions.

A further object of the invention is to provide an indexing apparatus wherein a tool can be safely locked in its operative position to withstand all such stresses which are anticipated during engagement of the tool with a workpiece.

An additional object of the invention is to provide the indexing apparatus with novel position selecting means for the tool holder and with novel drive means for rotating the tool holder at several speeds when the tool holder is unlocked so that it is free to assume a different angular position.

The invention is embodied in a machine tool, especially in a turning machine, which comprises a tool supporting holder which preferably constitutes a turret having sockets for a set of equidistant tools and is movable axially and indexible between a plurality of angular positions in each of which is different tool assumes its operative position, a stationary face gear which can be secured to a carriage for the holder, a second face gear which is provided on the holder and constitutes with the stationary face gear a detent structure capable of securely locking the holder in each of its angular positions, and a novel indexing apparatus which comprises shifting means for moving the holder axially between first and second positions in which the face gears are respectively in and out of mesh with each other. The shifting means includes a stationary clutch member which can be fixed to the aforementioned carriage and has an end face provided with at least one claw, a rotary second clutch member having at least one second claw which is slidable with reference to the first claw in response to rotation of the second clutch member whereby the second clutch member moves in the axial direction of the holder, and a motion transmitting sleeve which is externally threaded to mesh with internal threads of the second clutch member and is connected to the holder for axial movement therewith so that the holder moves axially when the second clutch member merely rotates as well as when the second clutch member rotates and simultaneously moves axially. The holder is then moved between its first and second positions. The indexing apparatus further comprises variable-speed drive means for rotating the holder in the latters second position and second drive means for rotating the second clutch member prior and subsequent to rotation of the holder to respectively move the holder to its second and first positions. A package of dished springs or an analogous biasing means is provided to urge the holder to its second position and to thus urge the claw or claws of the second clutch member against the claw or claws of the first clutch member.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved indexing apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic side elevational view of a machine tool having a turret-shaped tool holder which is indexible by an apparatus embodying one form of the present invention;

FIG. 2 is an enlarged fragmentary transverse vertical sectional view as seen in the direction of arrows from the line IIII of FIG. 1, showing the mechanical and certain electrical and hydraulic component parts of the indexing apparatus for the holder but with the tools omitted;

FIG. 3 is a diagram of the electric circuitry of the indexing apparatus;

FIG. 4 is a diagram of the hydraulic system of the indexing apparatus;

FIG. 5 is a table showing the code which is employed in the position selecting system of the indexing apparatus;

FIG. 6 is an elevational view of a valve member in the hydraulic system of the indexing apparatus;

FIG. 7 is an enlarged fragmentary developed view of claws on the clutch members of the indexing apparatus;

FIG. 8 is a diagrammatic developed view of a carrier for position selecting cams in the indexing apparatus;

FIG. 9 is an elevational view of one of the cams; and

FIG. 10 is a similar view of the cam of FIG. 9 but in another angular position.

4 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a machine tool which includes an indexible turret-shaped tool holder 1. The machine tool is a turning lathe having a base or bed 2 provided with horizontal ways 2a for a first or lower carriage 3 which is reciprocable at right angles to the axis of a rotary work spindle 6. The carriage 3 has horizontal ways 3a for a second or upper carriage 4 which supports the indexible tool holder 1 and is movable along the ways 3a in parallelism with the axis of the work spindle 6. The latter is rotatable in an upwardly extending headstock 5 of the base 2 and serves to receive a workpiece (not shown) which is rotated during engagement with a selected tool on the holder 1. The reference character 7 denotes a gripping or clamping aneclhanism which can actuate the chuck of the work spindle 6 to either engage or release a workpiece.

The apparatus for indexing the tool holder 1 is constructed in accordance with a feature of the present invention. The purpose of such indexing apparatus is to bring about a rapid movement of a selected tool to an operative position and accurate positioning of such selected tool in its operative position. The tool which is shown in FIG. 1 as occupying such operative position is denoted by the reference character 8.

FIG. 2 shows that the tool holder 1 is connected with a rotary and axially movable shaft 20 which is mounted in the upper carriage 4. The axis of the shaft 20 is normal to the axis of the work spindle 6. A driven element in the form of a ring 40 is fixedly secured to the shaft 20 by means of a key 40a. The ring 40 can be coupled for rotation with a driving element in the form of a worm wheel 44 by means of a claw clutch 38. The worm wheel 44 can be rotated, with the ring 40, shaft 20 and tool holder 1, by a worm shaft 26 which can be driven by a reversible hydraulic motor 10 shown in FIG. 4. The righthand end portion of the shaft 20 extends into a composite valve housing 46 which is movable axially with the shaft 20 but is held against rotation with reference to the carriage 4 by a post 47. The valve housing 46 accommodates a disk-shaped valve member 19 which is secured to the shaft 20 by a key 19a so that it shares all angular movements of the tool holder 1. The configuration of the valve member 19 is shown in FIGS. 4 and 6. The valve member 19 forms part of the control means for the motor 10 which serves to rotate the worm 26, i.e., to turn the shaft 20 and the tool holder 1 to one of eight different angular positions in each of which a different tool assumes an operative position.

The detent means for accurately locating and locking the tool holder 1 in a given angular position in which a selected tool on the tool holder is maintained in its operative position comprises a ring-shaped face gear 41a on the tool holder 1 and a stationary face gear 41 on the carriage 4. When the teeth at the left-hand side of the gear 41 mesh with the teeth at the right-hand side of the gear 41a, the tool holder 1 is maintained in one of several predetermined angular positions and the gears 41, 41a then prevent uncontrolled angular displacements of the tool holder 1 from the selected position. The worm 26 can rotate the shaft 20 and the tool holder 1 only when the teeth of the stationary gear 41 are out of mesh with the teeth of the gear 41a on the tool holder, i.e., in one of two axial positions of the tool holder. The means for shifting the shaft 20 axially so as to move the teeth of the face gear 41a into or out of mesh with the teeth of the fixed face gear 41 comprises a rotary clutch member here shown as a spur gear 30 the left-hand end face of which (as viewed in FIG. 2) is provided with claws or jaws 32 movable into and out of engagement with the complementary claws 33. The claws 3-3 are provided on a cylindrical clutch member 50 which is bolted, screwed or similarly fastened to the upper carriage 4. The clutch member or spur gear 30 can be rotated about the axis of the shaft 20 by a toothed rack 17 which meshes with its gear teeth 31. The claws 32 are biased axially of the shaft 20 and against the claws 33 of the clutch number 50 by a biasing means here shown as a pack-age of dished springs 35 which bear against a shoulder on a boss of the shaft 20 and react against an internal shoulder of a drum 39 which is rigid with the worm wheel 44 so that the springs 35 urge the shaft 20 in a direction to the left, as viewed in FIG. 2. The claws 33 are separated from each other by spaces 37 (see FIG. 7) which can receive the claws 32 of the gear 30. When the spaces 37 receive the claws 32, the package of springs 35 has moved the shaft 20 in a direction to the left (arrow A in FIG. 2) so that the teeth of the gear 41a on the tool holder 1 are disengaged from the teeth of the stationary gear 41; the tool holder 1 is then ready to be indexed to a different angular position in response to rotation of the worm 26.

The gear 30 is further provided with internal threads 34 which mesh with the external threads of a motion transmitting sleeve 48 which is held against axial movement with reference to the shaft 20. The sleeve 48 rotatably surrounds the corresponding portion of the shaft 20 and is non-rotatably mounted in the clutch member 50 by one or more keys 49. These keys enable the sleeve 48 to impart axial movements to and to share the axial movements of the shaft 20 with reference to the clutch member 50'.

When an indexing operation is completed, i.e., when a selected tool on the tool holder 1 is moved to its operative position, the teeth of the face gear 41a on the tool holder 1 can be returned into mesh with the teeth of the fixedly mounted face gear 41 in response to rotation of the gear 30 with reference to the clutch member 50 to such an extent that the claws 32 are expelled from the spaces 37. This brings about an axial movement of the shaft 20 and tool holder 1 in a direction to the right as indicated by the arrow B shown in FIG. 2. As shown in FIG. 7, the claws '32 and 33 are provided with suitably inclined cam faces 36 and 36a which enable the claws 32 to move out of the adjacent spaces 37 in response to rotation of the gear 30 relative to the clutch member 50 and its claws 33. Those axial movements of the gear 30 which are needed to expel the claws 32 from the spaces 37 take place against the opposition of the package of dished springs 35 which constitute a means for permanently biasing the shaft 20 and the tool holder 1 in a direction to maintain the gears 41, 41a of the detent means out of engagement with each other.

The improved indexing apparatus for the tool holder 1 is capable of insuring the retention of a selected tool in its operative position with a substantial force and such indexing apparatus is further capable of moving a selected tool to its operative position with a minimum of delay so that the periods of idleness between successive material removing operations can be reduced with attendant increase in the output of the machine tool. The indexing apparatus provides a self-locking action which insures that the gears 41, 41a automatically hold the selected tool in its operative position with a force which suffices to prevent uncontrolled displacements of the selected tool during engagement with the rotating workpiece which is held in the chuck of the work spindle 6 by the clamping mechanism 7 of the machine tool. The aforementioned internal threads 34 of the gear 30 enable the indexing apparatus to effect an axial motion of the tool holder 1 in connection with the action of the claws 32 and 33 in the following manner.

When a selected tool is to be indexed into the proper position, then first the gears 41, 41a must be disengaged. To this purpose the tooth rack 17 is moved towards the left according to FIG. 4, whereupon the gear 30 is turned in the direction of the arrow in FIG. 7 towards the left and the faces 32a of the claws 32 slide along the faces 33a of the claws 33 without the gear 30 altering its axial position. However, the shaft 20 carries out a small axial motion in the direction of the arrow A (FIG. 2) by turning the sleeve 48 by means of the thread 34 to slightly disengage the gears 41, 41a. As the claws 32 slide along the cam faces 36 a fast axial motion is under the action of the dished springs 35 achieved, this fast axial motion being superimposed on the axial motion resulting from the turning of gear 30. Now the gears 41, 41a are fully out of engagement.

When the selected tool has reached its proper position by turning of the worm gear 26 acting on the indexing drum 39, the aforementioned motions are reversed in order to effect a full engagement of the gears 41, 41a and thus to achieve an accurate adjustment in axial and circumferential direction. This operation is initiated by switch 9. First the toothed rack 17 is moved in opposite direction according to arrow B, whereby the gear 30 is turned together with the claws 32. The claws 32 then slide along the inclined cam faces 36 in opposite direction until the front faces 32a, 33a located in planes normal to the axis of the shaft 20 engage each other. This bao'kward motion of the claws 32 also pulls the shaft 20 and the tool holder 1 bacfkwards.

However, there is no full engagement of the gears '41, 41a as yet. This is achieved by an additional angular motion of gear 30 under the action of the toothed rack 17, this angular motion being transposed into a comparatively small axial motion by means of thread 34, so as to press the gears 41, 41a together. In order that there is full engagement and thus a highly accurate adjustment of the tool holder 1 in axial and circumferential direction, the clutch 38 has some circumferential play with the result that the teeth of both gears 41, 41a are then in complete mesh.

The threaded connection of the sleeve 48 and gear 30 insures a highly satisfactory self-locking action. The inclination of the threads on the parts 30 and 48 can be readily selected in such a way that the holder 1 can be held against rotation in response to substantial stresses during removal of material from a workpiece.

The gear 30 and the complementary clutch member 50.exhibit the important advantage that their claws can be machined at a relatively low cost. This is attributable to the provision of flat front faces 32a, 33a on the claws.

The clutch 38 exhibits the important advantage that the remaining parts of the variable-speed drive means for the tool holder 1 need not be disengaged when the tool holder is to be moved axially in response to rotation and/ or axial movement of the gear 30.

The automatic control system which responds to a signal from the programming unit of the machine tool and serves to move a selected tool to its operative position comprises the aforementioned drum 39 which constitutes a carrier for a set of nine cams 39a which are illustrated in developed View in FIG. 8 and respectively serve to actuate switches 61, S2, S3, S4, S5, S6, S7, S8, S9 provided in a switch housing 51. One of the switches S1-S9 is denoted in FIG. 2 by the reference character 45. The switches S1-S4 serve to select the positions of the tool holder 1 and the switches S5-S8 serve to select the direction of rotation of the tool holder. The drum 39 is rigidly secured to or integral with the worm wheel 44. The just described construction of the drum 39 and the mounting of switches S1-S9 in the form of a row render it possible to employ a very simple decoding device which selects the direction of rotaton of the drum 39 in order to reduce the length of the interval for selection of a particular tool to a minimum. It is clear, however, that the indexing apparatus can employ other types of decoding devices, especially if the tool holder 1 is to support a relatively small number of tools.

The two axial end positions of the tool holder 1 and its shaft 20 are scanned and indicated by a spring-biased plunger 42 which is mounted in the upper carriage 4 and abuts against the gear 41a. The plunger 42 itself being actuated by rack 17 constitutes an actuating device for a limit switch 43 which is mounted in the housing 51 and corresponds to the switch S10 shown in the circuit diagram of FIG. 3.

The manner in which the indexing apparatus can place a selected tool into the operative position will be described with reference to FIG. 3 which illustrates the electric circuit and with reference to FIG. 4 which illustrates the hydraulic system of the indexing apparatus. The selector means for the angular positions of the tool holder 1 further includes four electric switches I, II, III, IV which are shown in FIG. 3 and are respectively connected in circuit with relays A, B, C and D. The switches I-IV are actuated by the digital programming or control unit of the machine tool. In such programming unit, the switches I-IV are respectively represented by codes corresponding to those for decimal digits 1, 2, 4 and 8 (see the table of FIG. 5). The actuation of one or more switches I-IV results in energization of the respective relays A-D. The table of FIG. 5 shows that at least one of these relays is energized whenever the indexing apparatus is started in order to place one of the eight tools carried by the holder 1 into its operative position so that such tool can remove material from a workpiece which is held in the chuck of the work spindle 6. The placing of any one of the eight tools shown in FIG. 1 into the operative position necessitates the energization of at least one of the relays A-D.

When the indexing apparatus receives a signal to place a particular tool into the operative position, the contact a, b, 0 and/or a of the respective relay A, B, C and/or D completes an electric circuit in such a way that the switch S5, S6, S7 and/or S8 completes the circuit of one of two electromagnets M1, M2. The electromagnet M1 or M2 can be energized only in response to closing of a contact e by a further relay E. The contact e is closed when the relay E is deenergized. The deenergization of relay E takes place only when the switches S 1, S2, S3, S4 assume those positions which do not correspond to the positions which are necessary to move the tool holder (1 to a new or diflerent angular position. The various combinations of the positions which the switches 81-54 must assume in order to effect rotary movements of the tool holder 1 to the corresponding angular positions are also shown in the table of FIG. 5.

The electromagnets M1 and M2 constitute the solenoids of an impulse type electromagnetically operated control valve 9 which is shown in FIG. 4. The control valve 9 regulates the flow of pressurized hydraulic fluid to the reversible motor 10 which can drive the worm 26 in either direction, depending upon whether it receives pressurized fluid by way of a supply conduit 27 or a supply conduit 28. The electromagnet M1 or M2 is energized simultaneously with a third electromagnet M4 (FIG. 3) which can adjust a directional control valve 11 in such a way that the latter admits pressurized hydraulic fluid against the surface 12 of a piston 13a in the cylinder 13 of a cylinder and piston unit. The piston 13a has a piston rod which constitutes the toothed rack 17. The hydraulic fluid is preferably oil and is furnished to the cylinder 13 and motor 10 by a pump 14 which is driven by an electric motor M and draws fluid from an oil tank 14a. The one or the other inlet of the motor 10 receives presurized hydraulic fluid simultaneously with admission of pressurized fluid to the cylinder 13; however, this does not automatically result in rotation of the worm 26 because the motor I10 can drive the worm only when it can discharge hydraulic fluid that is being admitted by way of the control valve 9 and supply conduit 27 or 28. One return conduit for the flow of hydraulic fluid from the motor 10 is shown at 15; this conduit is connectable by the valve 11 with a one-way valve or check valve 16. The motor 10 is also prevented from discharging fluid by way of the valve member 19 because the latter is shown in FIG. 4 as being held by the tool holder 1 in an idle or starting position. In such idle position, the passages or bores 21, 22 of the valve member 19 (see FIGS. 2 and 4) are not in communication with a throttling orifice or bore 23 of the valve housing 46 so that the fluid cannot flow into a return conduit 24 which communicates with the orifice 23. Thus, when the electromagnet M4 is energized, the directional control valve 11 admits pressurized fluid against the surface 12 of the piston 13a in the cylinder 13 so that the rack 17 moves in a direction to the left, as viewed in FIG. 4, to thereby actuate the limit switch S10 (FIGS. 3 and 4) corresponding to the limit switch 43 of FIG. 2. Closing of the limit switch S10 by the rack I17 (and more particularly by the plunger 42 of FIG. 2) results in energization of a fourth electromagnet M3 which controls a second directional control valve 18. This results in opening of the return conduit 15 and in connection of the check valve 16 with a conduit 25 which is connected with the cylinder 13 at the other side of the piston 13a. Consequently, the motor 10 is free to rotate the worm 26 and the valve member 19 is also set in rotary motion. Since the conduit 25 is connected with the check valve 16 which is held in closed position by pressurized fluid, the rotation of valve member 19 and the resulting movements of the passages 21, 22 into registry with the throttling orifice 23 cannot result in flow of fluid through the return conduit 24. In other words, all of the fluid which leaves the motor 10 must flow by way of the return conduit 15.

The just described mode of operation of the hydraulic system is desirable in order to prevent the flow of fluid between the supply conduits 27, 28 when one of the passages 21 or 22 registers with the orifice 23. Furthermore, such mode of operation insures that all of the pressurized fluid which is supplied to the motor 10 can enter a return conduit only by flowing through this motor. This prevents abrupt or jerky angular displacements of the tool holder 1, especially when the desired extent or angular displacement of the tool holder is such that one or more tools must move through the operative position before the selected tool reaches such operative position. Whenever a tool approaches the operative position (corresponding to the position of the tool '8 shown in FIG. 1), the orifice 23 registers with a passage 21 or 22 and this would normally affect the rate of fluid delivery to the motor I10. The pasages 2'1, 22 respectively communicate with the supply conduits 27, 28 and the orifice 23 is flanked by a pair of passages 21, 22 whenever a tool assumes its operative position.

Shortly before the tool holder 1 reaches a selected angular position, the switches Sl-S4 (FIG. 3) are actuated by the respective cams 3911 on the drum 39 in such.

a way that the positions of their movable contacts correspond to those determined by the signal which has initiated the operation of the indexing apparatus. Consequently, the relay E becomes energized and its contact 6 opens the circuit of the electromagnets M1, M3 or M2, M3. The deenergization of electromagnet M1 or M2 in response to opening of the contact 2 does not change the position of the spool in the control valve 9 because this valve is an impulse type valve so that its condition remains unchanged as long as it does not receive a different impulse (energization of electromagnetic M2 subsequent to preceding energization and deenergization of the electromagnet M1 or vice versa). Thus, the motor 10 continues to rotate the worm 26 in the desired direction. However, the deenergization of electromagnet M3 changes the position of the spool in the directional control valve 1 8 so that the latter blocks the flow of fluid from the motor 10 by way of the return conduit 15. Therefore, the fluid which leaves the motor 10 must flow by way of the valve member 19. Such flow of fluid by way of the valve member 19 can take place in one of the two ways, namely: In accordance with the first possibility, a passage 21 or 22 registers with the orifice 23 shortly before the valve member 19 reaches the desired angular position (see FIG. 6), depending upon whether the tool holder 1 rotates clockwise or anticlockwise. In accordance with the second possibility, deenergization of electromagnet M3 and the resulting change in the position of spool in the directional control valve 18 enables the valve 18 to connect the conduits 24 and 25 with a conduit 29 which can discharge hydraulic fluid directly into the tank 14a. If the motor rotates the valve plate 19 in the direction indicated by the arrow shown in FIG. 6, the extent to which the orifice 23 registers with the adjacent passage 21 diminishes gradually whereby the rate of fluid flow through the motor 10 decreases accordingly and the worm 26 rotates the worm wheel 44 and the drum 39 at a gradually diminishing speed. The motor 10 comes to a halt when the orifice 23 ceases to register with the adjacent passage 21. The valve member 19 then assumes the idle position which is shown in FIG. 4 in which the orifice 23 is flanked by the two nearest passages 21 and 22 of the valve member. The switch S9 produces a signal when the valve member 19 reaches such idle position to deenergize the electromagnet M4 in order to effect a return movement of the spool in the directional control valve 11 to its normal position. The conduit then admits pressurized fluid to the lefthand side of the piston 13a, as viewed in FIG. 4, so that the rack 17 is retracted and ceases to actuate the switch S10. It will be noted that the valve member 19 can assume eight different idle positions in each of which the bore 23 is located between a difierent pair of passages 21, 22 and in each of which a different tool dwells in its operative position. The conduits 27, 28, 24 and the orifice 23 in the housing 46 constitute a composite conduit in which the fluid flows when the motor 10 rotates the worm 26 and the holder 1 approaches a selected angular posi tion. The return conduit 24 contains a second check valve 16'.

The just described operation of the motor 10 and the resulting rotation of the worm 26 brings about the following movements of parts which are shown in FIG. 2:

When the rack 17 moves in a direction to the left, as viewed in FIG. 4, its toothed portion causes the clutch member or gear 30 to rotate in a counterclockwise direction as indicated by the arrow shown in FIG. 7. The claws 32 then move with reference to the claws 33 without any immediate change in the axial position of the gear 30 because the front faces 32a of the claws 32 slide along the front faces 33a of the claws 33. However, since the internal threads 34 of the gear 30 mesh with the external threads of the motion transmitting sleeve 48 which cannot move axially of the shaft 20, the shaft 20 moves axially in the direction indicated by the arrow A. The tool holder 1 shares such axial movement of the shaft 20. When the inclined faces 36 of the claws 32 begin to slide along the inclined faces 36a of the claws 33 and enter the adjacent spaces 37 in the left-hand end position of the rack 17, the claw clutch 38 becomes operative because the driven element or ring 40 is urged by the springs to move in a direction to the left, as viewed in FIG. 2. The springs 35 act on the ring by way of the shaft 20. The rotation of gear 30 in response to a leftward movement of the rack 17 to its end position results in accelerated movement of the tool holder 1 in the direction indicated by the arrow A because such movement is due in part to rotation of the gear 30 on the externally threaded motion transmitting sleeve 48 and to a greater extent to movement of the inclined faces 36 along the adjacent inclined faces 36a. In other words, the gear 30 moves axially as soon as the faces 36 begin to slide along the adjacent faces 36a. The shaft 20 must share all axial movements of the sleeve '48 which is held against rotation by the keys 49 so that it moves axially in response to rotation as well as in response to axial movement of the gear 30. It is preferred to connect the sleeve 48 with the clutch member 50 by a set of equidistant keys 49. When the claws 32 enter the adjoining spaces 37 between the stationary claws 33, the teeth of the face gear 41a on the tool holder 1 are out of mesh with the teeth of the 10 face gear 41 so that the detent means is inoperative and the drum 39 for the cams 39a can be rotated by the worm 26, i.e., by the hydraulic motor 10. The plunger 42 is then disengaged from the limit switch 43.

The motor 10 is thereupon started in the aforedescribed manner to rotate the worm wheel 44 and the drum 39. The clutch 38 is already engaged because the detent means is inoperative and this clutch rotates the shaft 20 in response to rotation of the worm wheel 44. The cams 39:: on the rotating drum 39 actuate the associated switches 81-89 in order to insure that the motor 10 rotates the drum in the desired direction and that the motor 10 is first decelerated and then arrested when the selected tool on the holder 1 reaches its operative position.

When the tool holder 1 reaches the selected angular position, the switch S9 produces a signal which initiates the actuation of detent means 41, 41a by causing the tool holder 1 to move axially in the direction indicated by the arrow B. This is caused by the rack 17 which is being retracted into the cylinder 13 whereby its teeth rotate the gear 30 in a clockwise direction (i.e., in a direction to the right, as viewed in FIG. 7). The inclined faces 36 of the claws 32 slide along the corresponding inclined faces 36a of the claws 33 but in the opposite direction so that the claws 32 are expelled from the spaces 37. The front faces 32a thus return into abutment with the front faces 33a so that the rotating gear 30 continues to move the tool holder 1 axially (arrow B) but at a greatly reduced rate in order to produce a strong and reliable locking action. The clutch 38 is disengaged and allows the teeth of the gear 41a to penetrate fully into the spaces between the teeth of the gear 41. Thus, the disengaged clutch 38 allows for proper engagement between the teeth of the gears 41, 41a even if these gears are not machined with utmost precision.

The electric circuit of the indexing apparatus is designed in such a way that the selected tool is moved to its operative position by the shortest possible route, i.e., the direction of rotation of the tool turret 1 is automatically determined in such a way that a selected tool reaches the operative position in response to angular displacement of the tool turret '1 through an angle which does not exceed 180 degrees. The operation of the direction determining means (i.e., of the means which determines the direction of rotation of the tool turret 1 in order to move the selected tool to its operative position) is based on the fact that the operative positions of two tools which are located diametrically opposite each other with reference to the axis of the tool holder 1 can be positively identified by using four switches S5, S6, S7, S8 each of which is open when one of the corresponding pair of tools is in operative position and is closed when the other tool of the respective pair is located in operative position. This is achieved by placing the switches SS-SS into the path of movement of four teams 39a each of which 'has a lobe extending along an arc of 180 degrees (see FIGS. 8, 9 and 10). The switch S5, S6, S7 or S8 then influences the directional control system in such a way that it causes the drum 39 to rotate in a clockwise direction when it is open and in a counterclockwise direction when it is closed, or vice versa. This insures that any selected tool can reach the operative position by the shortest possible route, i.e., Without necessitating a rotation of the tool holder 1 through more than 180 degrees. The condition of the corresponding switch S5, S6, S7 or S8 does not change during rotation of the tool holder 1 in one direction. This is shown in FIGS. 9 and 10. Since the sockets ll of the tool holder 1 are equidistant from each other and the tool holder 1 is provided with eight sockets 1', the angular distance which the tool holder must cover in order to move a preceding tool from operative position and the next-following tool to operative position equals 45 degrees. Therefore, the lobes of cams which cooperate with the switches 85-88 are angularly offset with reference to each other by 45 degrees (each such lobe extends along an arc of degrees). It is clear, however, that the lobes of the cams for the switches SS-SS can be aligned with each other (i.e., they need not be staggered in the circumferential direction of the drum 39) if the switches 85-89 are not disposed in a row which is parallel to the axis of the shaft 20 but are staggered circumferentially by 45 degrees. In such modified apparatus, the four switches S-S8 can also be actuated by a single cam having a lobe extending along an arc of 180 degrees, provided that the four switches are located in a common plane normal to the axis of the shaft 20.

As soon as one of the switches 55-88 is selected to determine the direction of rotation of the drum 39 during indexing of the tool holder 1 to a new position, its movable contact should not change its position during rotation of the drum 39 in one direction in order to move the selected tool to its operative position. FIGS. 9 and show one of the cams which cooperate with the switches SS-SS; this cam is assumed to be associated with the tools occupying on the tool holder 1 the positions one and five. If the tool occupying the position one is to be moved to its operative position (see the position of the tool 8 in FIG. 1), the drum 39 will be rotated in a counterclockwise direction, as viewed in FIG. 9, because such direction of rotation insures that the tool occupying the position one (i.e., the first socket 1') will reach the operative position in response to rotation of the tool holder 1 through a relatively small (acute angle).

If the drum 39 dwells in the position of FIG. 10 when the indexing apparatus receives a signal to move the tool occupying the position five to its operative position, the tool holder will be rotated in a counterclockwise direction, as viewed in FIG. 1, because the tool holder is then required to rotate through less than 180 degrees.

If the drum 39 and the tool holder 1 dwell in the angular positions indicated in FIG. 9 and the tool occupying the position five is to be moved to its operative position, the drum 39 must be rotated in a clockwise direction because the selected tool then reaches its operative position before the tool holder completes one-half of a revolution. The respective switch S5, S6, S7 or S8 is then actuated shortly before the selected tool reaches its operative position. Analogously, if the drum 39 dwells in the angular position of FIG. 10 and the tool occupying the pos tion one is to be moved to its operative position, the drum 39 must be rotated in a clockwise direction and the movable contact of the corresponding switch 58, S6, S7 or S8 is permitted to move outwardly shortly before the selected tool reaches its operative position while the tool holder 1 turns through less than 180 degrees. Such actuation of the switch S5, S6, S7 or S8 by the respective cam 39a of the drum 39 has no influence on the position of the spool in the control valve 9 because the combination of location detecting switches 81-84 has terminated the flow of current by way of the contact e. The actuation of the switch S5, S6, S7 or S8 shortly before the selected tool reaches its operative position takes place only when the drum 39 is rotated in one of the two directions (namely, clockwise as viewed in FIG. 9 or 10). As men tioned before, the lobes of cams 39a for the switches S5- S8 extend along arcs of 180 degrees but are angularly offset by 45 degrees (see FIG. 8).

The table of FIG. 5 indicates that the relays A and B can determine the operative positions of four tools which are mounted in adjacent (successive) sockets 1' of the tool holder 1. Each of the other four tools is located diametrically opposite one of the first four tools. Since the combinations of the relays A, B for the other four tools are identical with the combinations for the first four tools (compare the positions of relays A and B for the tools 1-4 and 58 of the table shown in FIG. 5), the tool holder 1 would rotate in the same direction for each pair of tools which are mounted opposite each other. Therefore, the electric circuit includes the relay C which insures that the tool holder 1 rotates in a first direction 12 if one of a pair of oppositely mounted tools is to move to its operative position and in a second direction if the other tool of such pair is to be moved to operative position.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. In a machine tool, particularly in a turning machine, the combination of a tool supporting holder movable axially and indexible between a plurality of angular positions in each of which a dilferent tool thereon assumes an operative position; a stationary face gear; a second face gear provided on said holder; and an indexing apparatus comprising shifting means for moving said holder axially between first and second positions in which said gears are respectively in and out of mesh with each other, said shifting means including a stationary clutch member having at least one claw, a rotary second clutch member having at least one second claw slidable with reference to said first claw in response to rotation of said second member whereby said second member moves in the axial direction of said holder, and a motion transmitting member movable axially with said holder and having external threads meshing with internal threads provided on said second member so that said motion transmitting member moves said holder between said first and second positions in response to rotation and axial movement of said second member and variable-speed *drive means operable to rotate said holder in said second position thereof.

2. The combination as defined in claim 1, wherein said second clutch member has an end face and said second claw is provided on said end face thereof.

3. The combination as defined in claim 1, wherein said claws have parallel front faces located in a plane which is normal to the axis of said holder and abutting against each other in said first axial postion of said holder.

4. The combination as defined in clai m 3, wherein at least one of said claws has an inclined cam face along which the other claw slides during a portion of rotation of said second clutch member to move said holder between said first and second positions.

5. The combination as defined in claim 1, wherein said indexing apparatus further comprises biasing means for urging said holder to said second position and for thereby biasing said second claw against said first claw.

6. The combination as defined in claim 1, further comprising second drive means for rotating said second clutch member.

7. The combination as defined in claim 6, wherein said second clutch member comprises gear teeth and said second drive means comprises a toothed member meshing with said second clutch member.

8. The combination as defined in claim 7, wherein said toothed member is a reciprocable rack.

9. The combination as defined in claim 1, wherein said tool holder comprises a shaft which is rotatable in said motion transmitting member.

10. The combination as defined in claim 9, further comprising means for holding said motion transmitting member against rotation with said shaft.

11. The combination as defined in claim 1, wherein said drive means comprises a driving element, a driven element rotatable with said holder, and second clutch means coupling said elements in the second position of said holder.

12. The combination as defined in claim 11, wherein said second clutch means is disengaged in the first position of said holder so that the latter can rotate within limits in said first position thereof.

13. The combination as defined in claim 1, wherein said drive means comprises a fluid-operated motor and said indexing apparatus further comprises control means for said motor including a valve member rotatable with said holder and arranged to regulate the flow of fluid for operation of said motor so as to automatically reduce the rotational speed of said holder when the latter approaches a selected angular position.

14. The combination as defined in claim 13, wherein said control means further comprises conduit means for circulating pressurized fluid through said motor, said valve member being arranged to throttle and terminate the circulation of fluid in said conduit means and to thus regulate the speed of rotation of said holder.

15. The combination as defined in claim 14, wherein said valve member has pairs of passages, one pair for each of said angular positions, and said conduit means is provided with a throttling orifice which is disposed between and is sealed from the respective pair of passages in the corresponding angular position of said holder, said orifice being in gradually decreasing communication with one of the respective pair of passages when said holder approaches a selected angular position and said conduit means further comprising return conduit means for spent fluid communicating with said orifice and a pair of supply conduit means for pressurized fluid, each of said supply conduit means communicating with a different passage of each of said pairs of passages and being connected with said motor.

16. The combination as defined in claim 1, further comprising second drive means for rotating said second clutch member in first and second directions to thereby move said holder to said first and second positions thereof, said second drive means comprising a fluid-operated cylinder and piston unit having a piston movable in a first direction to thereby move said holder to said first position upon operation of said variable speed drive means and in a second direction to thereby move said holder to said second position prior to operation of said variable speed drive means.

17. The combination as defined in claim 1, wherein said indexing apparatus further comprises position selecting means connected for rotation with said holder and switch means cooperating with said selecting means to produce a signal before said holder reaches a selected angular position.

18. The combination as defined in claim 17, wherein said switch means is arranged to furnish a second signal when said holder reaches a selected angular position.

19. The combination as defined in claim 18, wherein said selecting means and said switch means cooperate to produce a third signal whenever said holder assumes one 14 of said angular positions during rotation to said selected position.

20. The combination as defined in claim 17, wherein said variable-speed drive means comprises a fluid-operated motor and a hydraulic system for conveying fluid to and from said motor, said system comprising conduit means connected with said motor and directional control valve means provided in said conduit means, said indexing apparatus further comprising second drive means for rotating said second clutch member including a fluidoperated cylinder and piston unit having a piston movable between first and second end positions respectively corresponding to the first and second positions of said holder.

21. The combination as defined in claim 20, further comprising a pump for circulating the fluid through said motor and for supplying fluid to said cylinder and piston unit, said valve means being responsive to said first signal to assume a first position and to the movement of said piston to one of said end positions to assume a second position, said motor being connected with said pump in one position of said valve means.

22. The combination as defined in claim 21, further comprising a valve member rotatable with said holder and arranged to regulate the flow of hydraulic fluid between said motor and said pump.

23. The combination as defined in claim 22, further comprising check valve means in series With said valve means and said valve member.

24. The combination as defined in claim 21, wherein said switch means is arranged to furnish a second signal when said holder reaches a selected angular position and said system comprises second directional control valve means connected between said pump and said cylinder and piston unit and responsive to said second signal.

25. The combination as defined in claim 21, further comprising a control valve connected between said pump and said motor, said selecting means and said switch means cooperating to produce a third signal which actuates said control valve whenever said holder assumes one of said angular positions during rotation to the selected position.

26. The combination as defined in claim 25, wherein said control valve is an impulse type valve.

GIL WEIDENFELD, Primary Examiner U.S. Cl. X.R. 

